package edu.kjxy.worker0329;

import java.util.Scanner;

public class worker01 {

	public static int distance(int x1, int y1, int x2, int y2) {
		return (int)Math.sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
	}
	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		int x1 = in.nextInt();
		int y1 = in.nextInt();
		int x2 = in.nextInt();
		int y2 = in.nextInt();
		in.close();
		
		int c = distance(x1, y1, x2, y2);
		System.out.println(c);
	}

}
